The GM has a choice. And they can choose to honour the players' use of their ability, and what it shows about the fiction the players want. (As
@hawkeyefan has made clear, the players did not want to play out a fight with the Duke's soldiers.) Or they can choose not to do so.
It's the choice by the GM to impose their conception of the fiction, regardless of what ideas for it the players have evinced
including by use of PC-build-acquired abilities, that creates the "Mother may I" dynamic. Because for the players, they can have their desired fiction only if it conforms to the GM's imaginings.